As illustrated in FIG. 1, a prior art water faucet 10 has a spout 11, which is provided with a joint 12 fastened therewith for connecting the spout 11 with a water filter 15 via a connection pipe 14. The joint 12 is provided with a connection switch 13 for regulating the flow of water from the spout 11 or into the connection pipe 14. The water filter 15 has an outlet 16 from which the filtered water is let out over a sink 17. Such a prior art water faucet as described above is defective in design in that it is rather complicated in construction, and that it can not be used handily in conjunction with a water filter.